In US Patent Publication No. 2013/0180434 A1 which is owned by the common assignee hereof, it was taught to employ tri-iso-butylphosphate (“TIBP”) as an air detraining agent (or “defoamer”) in combination with one or more alkanolamines such as triisopropanolamine to obtain a uniform distribution in a cement additive product, so as to resist structural degradation of the defoamer caused by the harsh mill temperatures and the mechanical grinding process itself whereby cement is made by inter-grinding precursor materials.
However, the present inventors discovered that use of an aqueous, amine based cement grinding additive with phosphate based defoamers can create problems where polyvinylchloride (PVC) equipment, including pipes, valves, tanks, and other fittings, are used at the cement processing plant. Phosphate-based defoamers, such as TIBP, can degrade polyvinylchloride (PVC) by dissolving the plasticizers used in its manufacture, such as esters of polycarboxylic acids, phosphate esters, phthalate esters, and the like. TIBP may also dissolve plasticizers in natural rubber and rubber-based materials (e.g., BUNA-N, VITON rubbers).
Hence, the present inventors believe there is a need for selecting alternative defoamers that can provide a stable alkanolamine cement additive composition while at the same time enabling use of PVC equipment during cement manufacture.